The very high data rates envisioned for the 4G wireless systems in reasonably large areas do not appear to be feasible with the conventional cellular architecture due the spectrum usage above the 2 GHz band, where in-building radio penetration is heavily penalized.
The foreseen solution could be that of improving coverage by increasing the density of base-stations. However, this solution would be feasible only if costs incurred by network expansion could be counterbalanced by a proportional growth of new subscribers. This seems unlikely, being the penetration of cellular phones already high in developed countries.
Some technologies concerned with distributing the radio frequency (RF) signal of wireless communication standards through pre-installed cable connections have recently gained attention. One example is femtocell technology. FIG. 1 shows a conventional femtocell system. The basic idea of femtocells lies in providing in-house base stations (or Femtocell access points) connected with the operator's core network through broadband backhauling cables (twisted pairs, coaxial cables and optical fibers).
Femtocell access points (FAPs) are envisioned to provide radio coverage for any cellular protocol (GSM/UMTS, WiMAX and HSPA/LTE) on the air interface, and to use broadband connections such as optical fiber or digital subscriber lines (xDSL) as back-hauling. Compared to other techniques for increasing system capacity, the key advantages of femtocells are the reduced deployment cost for the service provider, and the increased indoor coverage (namely for spectrum allocation beyond 2 GHz). However, the femtocell paradigm unavoidably leads to face with several (still) open issues such as synchronization (especially if using Orthogonal Frequency Division Multiple Access—OFDMA—as access method), security, interference and mobility management. All these issues could be more efficiently handled by a centralized approach rather than by employing dislocated and likely uncoordinated FAPs.
U.S. Pat. No. 6,014,546 tackles the issue of in-building distribution of a RF wireless signal over commonly pre-installed low-bandwidth infrastructure, and discloses a method for the distribution of the reference synchronization signal to tune the local oscillators for frequency conversion of the wireless signal.
The Applicants observe that the prior art apparatuses for distributing wireless signals over cable infrastructures do not account for any reconfigurability issues as a necessary requirement when dealing with the multitude of cellular protocols that are currently coexisting over the air interface.